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United States Patent 4875847
Douris , ê et al. October 24, 1989

Twin-screw extruder having respective conical nose screw sections

Wenger , Ê et al. October 24, 1989

Abstract

A twin screw extruder which significantly reduces extruder wear through provision of separate, complemental, interfitted frustoconical screw and barrel sections adjacent the outlet end of the extruder barrel which create an even, bearing-type support for the rotating screws as material passes through the apparatus. In preferred forms, the screws are intermeshed along the majority of the extruder barrel, but diverge at the region of the final frustoconical screw sections and are received within respective complemental barrel sections; in this fashion the material being processed is split into juxtaposed, non-communicating streams, and thereby evenly flows around and supports the adjacent screw section to lessen the tendency of the screws to separate themselves and come into wearing contact with the surrounding barrel walls. The extruder can be used to process a wide variety of plant-derived materials, but is particularly useful for viscous substances (e.g., soy concentrates and isolates) which can be difficult to handle with mono-screw extruders.